One method of covering roofs with thin metal roofing sheet includes the use of standing seams, i.e. seams that are of a height such as to always extend above any water that may be present on the roof. Seams are known which are snapped together without being squeezed, for instance the seams according to U.S. Pat. No. 5,519,974 and U.S. Pat. No. 5,535,567 wherein after having been placed together, the sheets are interlocked either with or without a sealing strip in respective seams, as illustrated in U.S. Pat. No. 6,115,899, for instance. The sheets are fastened to the roof in said seams, therewith avoiding through-penetrating nails or screws. Known machines for roll-forming the seam-forming edges can normally only shape the edges on sheeting of uniform width. Transverse seams are undesirable, and it is possible to produce long sheets in this way. Long roofing sheets are sometimes produced with a machine that is lifted onto the roof. This enables direct production of roofing sheets that are able to cover a very wide roof, said sheets being taken from a strip-carrying reel. Because production is carried out on the roof, it is possible to handle sheets that are several tens of meters in length.
JP 905 21 25 illustrates a machine that can roll-shape the edges of sheets that taper towards one end thereof. Such sheets are used, for instance, to cover the roofs of circular buildings. However, this machine can only handle piece-wise sheets that have been cut and edged in other equipment.